The sitemap for this site gives the homepage a priority of 1, articles 0.7, the featured post 0.9, and marks listing pages as changing weekly and posts as monthly. I wrote that code. I was fairly pleased with the tidy little hierarchy.

Google's sitemap documentation contains this sentence:

Google ignores <priority> and <changefreq> values.

Not “may deprioritize.” Ignores. So half of my sitemap is decoration.

What Google does read

<lastmod>. But with a condition that is easy to skim past:

Google uses the <lastmod> value if it's consistently and verifiably (for example by comparing to the last modification of the page) accurate.

Verifiably is the operative word. Google fetches the page and compares. If your lastmod says a page changed yesterday and the content is byte-identical to last month, Google learns your lastmod is noise and stops trusting it, for every URL in the file. The document is specific about what counts as a change worth updating lastmod for: content, structured data, or links. Not a copyright year in the footer.

What this site's sitemap actually does

Each post's entry uses updatedAt if the frontmatter has one and publishedAt otherwise. So lastmod moves only when I deliberately set a date on a post, which is the behavior Google's condition wants. I cannot accidentally bump every post by touching a shared layout file.

The listing pages and the homepage take the date of the newest post, which is honest: the homepage did change when a new post appeared on it.

Draft posts are not in the sitemap at all. That is a separate problem I already wrote up in previewing drafts without leaking them to Google, and the sitemap only ever reads the published set.

Why I am leaving the ignored fields in

Removing priority and changefreq would be correct and pointless. They are valid XML, they do no harm, and other consumers of sitemaps do read them. The lesson is not to strip them. It is to stop thinking they do anything on Google, and to stop tuning them.

The temptation they create is the real risk. If you believe a priority of 1.0 helps, you will set everything to 1.0, which helps nothing. If you believe changefreq: daily makes Google crawl daily, you will set it and then feel ignored, which you are.

What a small site should do instead

Google's own advice for sites that are not large is brief: keep the sitemap up to date and check the Page indexing report in Search Console regularly. A sitemap is a hint about which URLs you want indexed. Submitting one does not guarantee a crawl, let alone indexing.

Two limits, for completeness: fifty thousand URLs or fifty megabytes uncompressed per file, after which you split into several and add an index. This site has twenty-eight URLs. That limit is not in my future.

The one field worth getting right

lastmod, tied to real changes. Everything else in the file is for you, not for Google.

Source: Google Search Central, “Build and submit a sitemap.”